1. Technical Field
The present invention generally relates to methods of controlling automatic transmissions in automotive vehicles and, more particularly, to a method of controlling a kick down gear change in an automatic transmission.
2. Discussion
Most modern automotive vehicles are equipped with an automatic transmission. The automatic transmission includes a plurality of gears for providing different ratios between engine speed and tire rotation. Depending upon which gear ratio is selected, different acceleration is provided.
Under certain circumstances, an operator of an automotive vehicle may accelerate in such a manner that a gear change is required. This is known in the art as a "kick down". In a kick down situation, the vehicle transmission shifts from one operating gear to a lower operating gear. For example, a kick down may take a four speed transmission from fourth gear to third gear, from third gear to second gear, or from second gear to first gear.
Conventional kick down gear changes are performed independent of throttle rate. That is, the speed at which the automatic clutch is engaged to perform the gear change is constant regardless of how quickly the driver presses on the accelerator. As such, if a driver quickly steps into the accelerator, the rate at which the automatic clutch is engaged is the same as if the driver just gradually steps into the accelerator.
While such conventional kick down techniques are generally satisfactory, there is room for improvement in the art. For example, it has recently been discovered that when a driver aggressively steps into the accelerator, the driver is typically passing another vehicle or otherwise desiring quick acceleration. On the other hand, when a driver gradually steps into the accelerator, a normal speed adjustment is occurring wherein slower acceleration is acceptable.
Thus, it would be desirable to provide a technique for engaging the clutch and switching gears at different speeds based on the rate at which the driver steps into the accelerator. In this way, a quick and aggressive gear change can be provided under passing conditions and a slow and smooth gear change can be provided under non-passing conditions. By distinguishing the needs of the vehicle based on the driver's rate of stepping into the accelerator, greater control of vehicle performance can be achieved.
Accordingly, it is an object of the present invention to provide a method of controlling the rate of a gear change in an automatic transmission based on the throttle rate demanded by the driver.